1. Field of the Invention
The present invention pertains to the art of microwave power dividers and combiners.
2. Art Background
Power dividers and combiners are widely used in high frequency radio frequency devices. They provide isolation between coupled ports by combining an input signal with an 180 degree (half wavelength) delayed version of the input signal at the isolated port. In this manner, signals are cancelled at the isolated port. Since isolation relies on wavelength-dependent delays, these devices are typically narrow-band in nature.
As standards in electronic devices evolve, so does the desirability to have them work on different frequencies. For example, cellular telephones in the United States may wish to support both analog services centered around 860 MHz and digital services centered around 1990 MHz. Other devices may wish to make use of both 928 MHz and 2.4 GHz bands. It is very difficult to produce couplers which operate over this wide a frequency range.
Power dividers/couplers have switchable path lengths to allow operation on multiple frequency bands while maintaining performance comparable to that of a single-band design. A Wilkinson-type design features switchable path lengths to support multiple frequency bands. A rat-race design features multiple races to support multiple frequency bands.